waltermixxx
Posts: 34
Joined: Wed May 09, 2012 7:21 pm
Location: Woodbridge, Ontario

Re: Modifying a 3.5" car display for USB power.

Thu Mar 07, 2013 9:27 pm

portablesounds wrote:@waltermixxx when i tried your power to usb cable my screen will only flicker for a millisecond, turn off, and repeat every few seconds. i think it may be due to the 5v to 12v regulator, considering power is coming through, or is it maybe bad soldering? My board is slightly different than everyone else's that has posted, but i believe i have found the correct converter, although my webcam is too crappy to give any good detailed photos. Hope someone has any idea as to what my problem is. Thanks! -portablesounds
could be the lcd tv you have actually does require 12 volts, that is to say the voltage regulator on it may not be a switching voltage regulator so it does requrie more than 5 volts, the regulator in my 3.5" tv appears to be a switching voltage regulator ( more than 3 pins ) and also has a very low voltage drop :) I think i got lucky with mine :) I did not think it would work when I tried it. but alas it did... :)
Electronics for fun...
Raspberry Pi-1 Occidentalist, Tenda 311m x 2
Raspberry Pi-2 Raspbian Wheezy 07-15-12, Netgear N150 x1
Genius 8000 slimline wireless keyboard and mouse both work great with the usb wifi dongle right in the raspberry pi.

LiamEdwards
Posts: 1
Joined: Sat Mar 16, 2013 2:54 pm

Re: Modifying a 3.5" car display for USB power.

Sat Mar 16, 2013 3:04 pm

[quote] marcialr[quote]

I have the same TFT monitor i am using a USB3 cable would this make all the differance because i can't get the screen to do anything

Aelin
Posts: 1
Joined: Tue Mar 19, 2013 12:56 am

Re: Modifying a 3.5" car display for USB power.

Tue Mar 19, 2013 12:57 am

Karamell, what exactly did you do there? The image makes it difficult for me to see.

portablesounds
Posts: 8
Joined: Wed Feb 27, 2013 1:11 am

Re: Modifying a 3.5" car display for USB power.

Wed Mar 20, 2013 11:26 pm

waltermixxx wrote:
portablesounds wrote:@waltermixxx when i tried your power to usb cable my screen will only flicker for a millisecond, turn off, and repeat every few seconds. i think it may be due to the 5v to 12v regulator, considering power is coming through, or is it maybe bad soldering? My board is slightly different than everyone else's that has posted, but i believe i have found the correct converter, although my webcam is too crappy to give any good detailed photos. Hope someone has any idea as to what my problem is. Thanks! -portablesounds
could be the lcd tv you have actually does require 12 volts, that is to say the voltage regulator on it may not be a switching voltage regulator so it does requrie more than 5 volts, the regulator in my 3.5" tv appears to be a switching voltage regulator ( more than 3 pins ) and also has a very low voltage drop :) I think i got lucky with mine :) I did not think it would work when I tried it. but alas it did... :)
So i guess i need to remove the regulator? Or is my unit really in need of 12v and the regulator makes no difference? I'm gonna test this out and post some pics and stuff afterwards. Hope this helps someone!

richard238
Posts: 108
Joined: Sun Mar 31, 2013 1:36 pm
Location: Crawley, UK

Re: Modifying a 3.5" car display for USB power.

Sun Mar 31, 2013 1:43 pm

Kronalias wrote:Here's a short video of my modded car display working with a Pi and Plugable usb hub:

http://www.youtube.com/watch?v=xhKaFuJ7A9o

I have an identical board, I've removed the chip, attached a 5v supply but get only a white screen.
I've tried several USB PSUs
The screen/monitor worked fine on 12v, so what then have I missed, why no display at 5v?
Thank you

magno23
Posts: 136
Joined: Sun Aug 12, 2012 4:11 pm
Location: Penafiel, Portugal

Re: Modifying a 3.5" car display for USB power.

Sun Mar 31, 2013 4:48 pm

richard238 wrote:
Kronalias wrote:Here's a short video of my modded car display working with a Pi and Plugable usb hub:

http://www.youtube.com/watch?v=xhKaFuJ7A9o

I have an identical board, I've removed the chip, attached a 5v supply but get only a white screen.
I've tried several USB PSUs
The screen/monitor worked fine on 12v, so what then have I missed, why no display at 5v?
Thank you
there is a unused 4 pin connector on the side of the board, try to find which on is the 5v pin and connect you power supply to it

richard238
Posts: 108
Joined: Sun Mar 31, 2013 1:36 pm
Location: Crawley, UK

Re: Modifying a 3.5" car display for USB power.

Sun Mar 31, 2013 9:16 pm

Done that, just get a white screen.

jward2305
Posts: 3
Joined: Sun Mar 31, 2013 12:28 am

Re: Modifying a 3.5" car display for USB power.

Mon Apr 01, 2013 2:19 am

Step 7? What is the purpose?

I found another tutorial on how to do this and it doesn't mention anything about removing the 5V and 12V capacitor? Take a look below
http://www.wisegai.com/2012/11/29/raspb ... using-usb/

Do they both work just as well?

richard238
Posts: 108
Joined: Sun Mar 31, 2013 1:36 pm
Location: Crawley, UK

Re: Modifying a 3.5" car display for USB power.

Tue Apr 02, 2013 1:04 pm

Running the monitor on 5v, I attached a compact digital camera.

The monitor still only shows white but displays also some colour banding as the camera moves about.
So there is life in there, I just need to know how to release it, please?

Thanks.

magno23
Posts: 136
Joined: Sun Aug 12, 2012 4:11 pm
Location: Penafiel, Portugal

Re: Modifying a 3.5" car display for USB power.

Tue Apr 02, 2013 1:23 pm

are you setting any stv_mode on the config.txt file?
I had that problem when i configured it for NTSC instead of PAL

richard238
Posts: 108
Joined: Sun Mar 31, 2013 1:36 pm
Location: Crawley, UK

Re: Modifying a 3.5" car display for USB power.

Tue Apr 02, 2013 6:09 pm

No change with an NTSC or PAL input, still just a white screen and vertical banding.

djt205
Posts: 2
Joined: Wed Apr 03, 2013 12:57 pm

Re: Modifying a 3.5" car display for USB power.

Wed Apr 03, 2013 1:04 pm

I have the same board as Richard and Kronalias and can confirm that mine does not work on 5v. There is a post on page 4 by AndyA explaining it.
Would love a diagram of how it taps into the switcher to generate the bias voltages.
I've returned the 3.5 to 12v operation now and will use it for something else. Now got a 4.3" one to try, will post back if it works.

djt205
Posts: 2
Joined: Wed Apr 03, 2013 12:57 pm

Re: Modifying a 3.5" car display for USB power.

Wed Apr 03, 2013 6:31 pm

Success with the 4.3" display!

One thing I noticed is that the supplied wires with the screen seem to have a fair bit of resistance and were dropping about 0.6v under load which gave the screen flashing on and off behaviour mentioned by someone else earlier in the thread. Also the path from the output of the 5v regulator to the input of the two smaller regulators had 0.6 ohms resistance, so I've attached my 5v feed nice and close to those with some better wire which has made it work perfectly. The screen stays working until about 4.4v, before which it has trouble detecting the signal. Video source is currently my Sega Nomad. Can someone give me a pointer about uploading higher quality images on here?
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richard238
Posts: 108
Joined: Sun Mar 31, 2013 1:36 pm
Location: Crawley, UK

Re: Modifying a 3.5" car display for USB power.

Thu Apr 11, 2013 9:31 pm

So, given my monitor is now useless, is it worth removing any of the other components to try and get it running on 5v?

Thanks.
Last edited by richard238 on Wed Apr 17, 2013 9:40 am, edited 2 times in total.

d5t
Posts: 3
Joined: Thu Apr 11, 2013 3:52 pm

Re: Modifying a 3.5" car display for USB power.

Thu Apr 11, 2013 10:08 pm

CidVilas wrote:Here is my successful attempt. Follows the instructions everyone else has, but could help someone else. Thanks to all, who have contributed!

I've included pictures of the patch and post fix display. Works great, and minimal work done to the display.
IMG_20130218_002615.jpg
IMG_20130218_002841.jpg
It looks like I've got pretty much the same board you have.
Image
So you basicly have just added a linking cable from the 5V+ of the plug to the 5V+ on the right without removing anything? Any Troubles so far?

Edit: I'd like to power the Display directly via gpio, but when I connect gpio pin 2 and 4 to the two pinholes on the right, the rpi instantly turns off and thats it.

richard238
Posts: 108
Joined: Sun Mar 31, 2013 1:36 pm
Location: Crawley, UK

Re: Modifying a 3.5" car display for USB power.

Wed Apr 17, 2013 9:41 am

richard238 wrote:So, given my monitor is now useless, is it worth removing any of the other components to try and get it running on 5v?

Thanks.
Bump! Anyone, any ideas, please?

fdufnews
Posts: 289
Joined: Fri Oct 07, 2011 5:37 pm

Re: Modifying a 3.5" car display for USB power.

Wed Apr 17, 2013 11:33 am

I'd like to power the Display directly via gpio, but when I connect gpio pin 2 and 4 to the two pinholes on the right, the rpi instantly turns off and thats it
Crazy idea!!! You can consider you lucky if the Pi is still alive.
The GPIO can't source enough current to power any screen.

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dasimpson
Posts: 311
Joined: Fri Jun 29, 2012 2:17 pm

Re: Modifying a 3.5" car display for USB power.

Wed Apr 17, 2013 11:44 am

yes try a 6 volt battery for the screen I had this same problem with my first screen I ended up using a dc-dc boost converter
richard238 wrote:
richard238 wrote:So, given my monitor is now useless, is it worth removing any of the other components to try and get it running on 5v?

Thanks.
Bump! Anyone, any ideas, please?

User avatar
dasimpson
Posts: 311
Joined: Fri Jun 29, 2012 2:17 pm

Re: Modifying a 3.5" car display for USB power.

Wed Apr 17, 2013 11:45 am

on the rev 2 pi they can power then screen easy thru the gpio I do it in my mod with out any problems the only problem I had is my dc boost converter was not quite upto the job but using a 3 amp 5 volt power supply it worked perfectly
fdufnews wrote:
I'd like to power the Display directly via gpio, but when I connect gpio pin 2 and 4 to the two pinholes on the right, the rpi instantly turns off and thats it
Crazy idea!!! You can consider you lucky if the Pi is still alive.
The GPIO can't source enough current to power any screen.

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dasimpson
Posts: 311
Joined: Fri Jun 29, 2012 2:17 pm

Re: Modifying a 3.5" car display for USB power.

Wed Apr 17, 2013 11:48 am

take a multi meter check the 4 pins far right the top pin should be 5v+ the next down common ground 5v- the 2 below are data lines don't use them if your pi shuts off then your power supply might not be upto the ampage rating needed with pi and screen you will be looking at close to 1.5amp from my experience
d5t wrote:
CidVilas wrote:Here is my successful attempt. Follows the instructions everyone else has, but could help someone else. Thanks to all, who have contributed!

I've included pictures of the patch and post fix display. Works great, and minimal work done to the display.
IMG_20130218_002615.jpg
IMG_20130218_002841.jpg
It looks like I've got pretty much the same board you have.
Image
So you basicly have just added a linking cable from the 5V+ of the plug to the 5V+ on the right without removing anything? Any Troubles so far?

Edit: I'd like to power the Display directly via gpio, but when I connect gpio pin 2 and 4 to the two pinholes on the right, the rpi instantly turns off and thats it.

Gwyn400
Posts: 33
Joined: Fri Jul 20, 2012 1:49 pm

Re: Modifying a 3.5" car display for USB power.

Thu Apr 18, 2013 9:50 am

Will this also work for a 4.3" monitor such as this one? http://www.ebay.co.uk/itm/181085381340? ... 1497.l2649
Complete noob

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dasimpson
Posts: 311
Joined: Fri Jun 29, 2012 2:17 pm

Re: Modifying a 3.5" car display for USB power.

Thu Apr 18, 2013 11:44 am

Gwyn400 wrote:Will this also work for a 4.3" monitor such as this one? http://www.ebay.co.uk/itm/181085381340? ... 1497.l2649
it is a bit hit and miss to ones that do work and ones that don't on the 5 volt mod they is sevral different pcb layouts

fdufnews
Posts: 289
Joined: Fri Oct 07, 2011 5:37 pm

Re: Modifying a 3.5" car display for USB power.

Thu Apr 18, 2013 7:36 pm

on the rev 2 pi they can power then screen easy thru the gpio
OK, I think your talking about the power pins on the extension connector.
GPIOs are logic input/output that you adress through software. GPIO can't source many current.
Concerning the +5V on the extension connector since rev2 there is no more limitation on the current that can be sourced by those pins as the polyfuse has been removed

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dasimpson
Posts: 311
Joined: Fri Jun 29, 2012 2:17 pm

Re: Modifying a 3.5" car display for USB power.

Thu Apr 18, 2013 7:53 pm

ah get your meaning I thogt they just called that hole area the gpio section

Gwyn400
Posts: 33
Joined: Fri Jul 20, 2012 1:49 pm

Re: Modifying a 3.5" car display for USB power.

Mon Apr 22, 2013 10:25 am

I bought that 4.3" one from eBay but I'm a bit of a noob when it comes to this kind of thing so would someone be able to point out what needs removing and what needs soldering where from this picture? I can get a better/clearer picture if needed
Image

[EDIT] Never mind, I recently bought a plug with several different interchangeable attachment things and one of them happened to be the right size for the screens power input, so I soldered an old USB to that attachment, plugged it in and it worked instantly from USB with no changes at all to the screen.
So I recommend the screen in my previous post for any noobs like me
Here it is being powered by my laptop (with my GameCube because my Pi isn't nearby)
Image
Complete noob

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